Oil-well drilling presents a unique industrial-waste-control and energy-saving problem because geologists and engineers must locate drilling rigs and related services as close as possible to where the oil or gas is believed to occur--not where it is convenient, as in the case of a plant site. Secondly, hundreds and usually thousands of feet of clay, sandstone or limestone rock must ordinarily be removed by the drill bit and circulating mud before personnel on a rig know whether they were successful. In deep wells, a carload of cuttings are brought to the surface every 8 hours.
Several thousand barrels of mud and chemicals are required to drill to target depth successfully. Once this task has been completed, all of the mud, cuttings, decomposed and altered organic and inorganic by-products and accumulated debris is on the surface in pits. Better methods than allowing such waste to remain in a pit or having trucks come in to haul it all off are needed.
According to an established and accepted method of drilling on land, drilled cuttings, waste mud and excess drilling fluid are stored in temporary earthen pits while the well is being drilled. The pits are typically constructed by having a bulldozer push up dikes prior to starting drilling operations. The pit is connected to a circulating system of the rig by pipe or ditches. (See FIGURE.)
Once drilling begins, circulation of enormous quantities of water is a necessary part of the drilling operation. Hand-in-hand with the water used to make a drilling mud is the subsequent generation of, literally, carloads of drill cuttings brought to the surface by the drilling mud. The spent mud and cuttings are deposited in the diked areas (reserve pits).
The earthen pits may cover an acre or more. In some deep wells or wells of large borehole diameter the waste pits (called reserve pits by many in the industry) may contain 50,000 to 100,000 barrels (bbl) of such spent drilling mud and cuttings.
In cases of limited available land for pits, the whole waste-mud slurry may be hauled off once or twice while the well is being drilled. This great expense seriously affects the efficiency of the whole drilling operation. These current practices are a source of wasted manpower, equipment and energy.
Therefore, those in the industry recognize that a method to improve this aspect of the drilling operation would be highly desirable. Based on this premise, a formulation of chemicals, procedures and equipment has been developed to allow recycle of a major part of the waste fluid; restoration of the land where a pit is located is thus greatly simplified.
The effect is a net reduction in energy use and a great reduction in potential adverse effects on the environment for years to come in the area around mud storage pits, as well as a reduction in damage to streams and ponds due to surface run-off.
Thus, after a well is drilled, and regardless of whether it produces commercial quantities of oil or gas, this invention permits restoration of the land by conventional earth movers so that the surface can once again be used for farming or as range land for animals.
Specifically this invention pertains to a new practical method of treating waste mud and drilled cuttings while still in temporary earthen pits by the use of formulated chemicals along with a specific procedure so that the water therein is substantially separated from solids. This permits recycling clarified water and restoring the land to the condition it was in prior to drilling the well.